1. Field of the Invention
The present invention relates to a lens barrel, an imaging device body, and an imaging device that include an apodization filter.
2. Description of the Related Art
There is known an imaging device that includes an apodization filter (hereinafter, referred to as an APD filter) having optical characteristics in which light transmittance is reduced as a distance from an optical axis is increased (see JP1997-236740A (JP-H09-236740A) and JP2012-128151A). The APD filter reduces the amount of a ray around only a blurred image (spotlight blurring or the like), which is out of focus, without reducing the amount of a ray around an image plane. Accordingly, the APD filter realizes a beautiful blur by applying gradation to the profile of the blurred image.
In the imaging device including the APD filter, the APD filter is disposed near a diaphragm (see JP-H09-236740A) and JP2012-128151A). In JP1997-236740A (JP-H09-236740A), the APD filter is disposed near the diaphragm on the light-incident side or the light-emitting side of the diaphragm in order to reduce the vignetting of a ray deviating from the optical axis. In JP2012-128151A, the APD filter is disposed near the diaphragm on the light-emitting side of the diaphragm in order to reduce the dependency of an angle with respect to the optical axis of luminous flux of incident rays on the effect of the APD filter.
Since the APD filter cannot be disposed at the same position as the diaphragm in principle even though the APD filter is disposed near the diaphragm as disclosed in JP1997-236740A (JP-H09-236740A) and JP2012-128151A, the APD filter is disposed at a position that is shifted from the diaphragm in the direction of the optical axis. In a case in which incident luminous flux is parallel to the optical axis, an upper ray and a lower ray of the luminous flux (parallel luminous flux) are incident on positions of the APD filter that have the same light transmittance. Accordingly, the APD filter uniformly applies gradation to the profile of a blurred image. In contrast, in a case in which incident luminous flux is not parallel to the optical axis, an upper ray and a lower ray of the luminous flux (oblique luminous flux) are incident on positions of the APD filter that have different light transmittances. Accordingly, the APD filter non-uniformly applies gradation to the profile of a blurred image. As a result, a deviation is generated in the blurred image.
The generation of a deviation in a blurred image in the case of oblique luminous flux will be described with reference to FIG. 11. In FIG. 11, an APD filter 118 is disposed on the light-emitting side of a diaphragm 116 and oblique luminous flux, which is obliquely incident on the diaphragm 116 from the upper side of an optical axis, is shown.
In this case, an upper ray L102, which passes through an upper end of the aperture portion of the diaphragm 116, passes through a position that is closer to the center of the APD filter 118 than the position through which an upper ray of parallel luminous flux passes. On the other hand, a lower ray L103, which passes through a lower end of the aperture portion of the diaphragm 116, passes through a position that is more distant from the center of the APD filter 118 than the position through which a lower ray of parallel luminous flux passes. The center of the APD filter 118 corresponds to the optical axis and the light transmittance of the APD filter 118 is reduced as a distance from the center of the APD filter 118 is increased. Accordingly, the amount of the upper ray L102 reduced by the APD filter 118 is smaller than the amount of the lower ray L103 reduced by the APD filter 118. Accordingly, a deviation is generated in a blurred image of the oblique luminous flux in a vertical direction.